<!doctype html>
<html>
<head>
  <style>
    #container {
      height: 300px;
      width: 300px;
      overflow:hidden;
      border-radius:30px;
      opacity: 0.6;
    }
    #inner {
      width: 380px;
      height: 260px;
      background-color: #00ff00;
    }
  </style>
</head>
<body>
  <div id="container">
    <div id="inner">
    </div>
  </div>
</body>
</html>
